Rotating contact device



Jan. 12, 1943. c. J. HAYNES ROTATING CONTACT DEVICE Filed Dec. 28, 1939 Patented Jan. 12, 1943 ROTATING CONTACT DEVICE Cecil J.

Haynes, Houston, Tex., assignor to Standard Oil Development Company, a corporation of Delaware Application December 28, 1939, Serial No. 311,24&

2 Claims.

This invention relates to apparatus for logging wells, such as oil wells, and more particularly to an electrode adapted for use for determining the nature of the strata of the earth through which a well is bored. I

Methods and apparatus for logging wells are well known. Examples of apparatus for this purpose are disclosed in U. S. Patents Nos. 2,137,306, issued April 14, 1936, to Blau et al., and 2,132,807, issued October 11, 1938, to Rust et al.

The present invention relates to the construction of an electrode adapted for use in systems like that described in the above mentioned patents or in other well logging operations in which the impedance or resistance or potential or some other electrical characteristic of the formations or strata adjoining a well are being determined or compared.

The present invention is particularly directed to an electrode which is suitable for logging a well which has been drilled by the use of an oil base drilling fluid. At the present time most wells are drilled with the aid of a water base drilling fluid, but oil base drilling fluids offer substantial advantages under some conditions and their use is growing in popularity.

It well known to the art that in drilling bore holes involving a drilling fluid the solids carried by the drilling fluid form a coating or flltercake along the bore of the hole. When oil base drilling fluids are used in drilling operations, the fllter cake on the side of the bore hole has non-conducting characteristics due to the fact that the liquid phase comprises non-conducting oil.

Most of the present processes of logging wells involve the lowering of an electrode into the bore hole at the end of a cable and then passing current down through the cable to the electrode where it is conducted through the drilling mud to the formations surrounding the bore hole and from there the circuit is completed by the current passing up to the surface of the earth through the geologic formations, the variation in magnitude of the current as the electrode moves in the bore hole being recorded. It will be apparent that, when a well has en drilled with an oil base drilling fluid, the use tordinary electrodes will cause difficulty in that little or no current will pass through the non-conducting filter cake formed on the side of the bore hole.

To overcome this difficulty in well logging it is an object of the present invention to provide an electrode which will make direct contact with the geologic formation penetrated by the bore hole.

It is anotherobject of the present invention to provide an electrode which will make direct contact with the formations encountered in the bore hole and which will adjust itself to varying diameters of a bore hole.

It is a further object of the present invention to provide an electrode equipped with toothed disks mounted so that the teeth of the disks penetrate through the filter cake on the side of the hole and make contact with the geologic formations.

Other objects and advantages of the present invention will be apparent from the following description taken in connection with the accompanying drawing in which Fig. 1 is a vertical cross-sectional view of a section of a bore hole showing the electrode in position therein and illustrating diagrammatically a reel and an electrical apparatus at the surface of the earth for logging the variations of some property of the formation around the .well as the electrode is moved therein;

Fig. 2 is an enlarged view of the electrode shown in Fig. 1; and i Fig. 3 is a cross-sectional view taken along the line III-III of P18. 2.

Referring to the drawing in detail and first to Fig. 1 it will be seen that a bore hole is illustrated at l, the bore hole having an electrode designated generally as 2 therein, the electrode being suspended by means of an insulated electrical conductor cable 3 which is attached to a hoist 4 at the well head. The hoist is provided with a slip ring 5 to which a contact member 6 is attached, which, in turn, is attached to electrical apparatus within a box represented diagrammatically by 1. To complete the electrical circuit the apparatus within box I may be grounded by any suitable means such as a conductor 8 attached to ground 9.

The apparatus within the box 1 is well known to those skilled in the art and need not be described herein since it forms no part of the present invention. By way of example it may be said, however, that the apparatu may be similar to that shown in the Blau et al. or Rust et al. patents above referred to or it may consist of a means for producing a current combined with a sensitive volt meter or potentiometer or other similar means for measuring electrical characteristics.

The electrode itself which forms the subject matter of the present invention comprises two disks ll free to rotate around shafts II which, in turn, are mounted on springs l3. Telescoping tubes I 4 have springs I3 attached to them, each end of the tubes having one end oi each spring secured thereto. In addition, the lower end of telescoping tubes I4 is provided with a tip l5 which serves both to protect the equipment against shocks and acts as a guide.

As will be seen from the drawing, springs l3 are bent outwardly so that they will force the periphery of disks ll against the wall of a bore hole when the device is lowered into a hole.

The upper end of tubes l4, the upper ends of springs l3, and the lower end of conductor l I are all attached to cylindrical block l8 which is constructed of a material which is a good electrical conductor. Conductor I1 is covered with insulating material IS, the conductor and insulating material comprising cable 3. .By means of the above described construction an electric current may flow through disk ll, shaft l2, spring l3, block l8 and conductor I! to the apparatus arranged on the surface of the earth.

It is desirable to provide disks H with teeth, as shown in the drawing, so that better penetration through the mud pack or filter cake lining the bore hole will be obtained. If teeth are provided, any suitable shape may be used, for example conically shaped teeth are very satisfactory. On some occasions, it may be desirable to dispense with the teeth and provide the periphery of disks 1 I with sharp edges which will be forced into the sides of the bore hole by the springs l3.

It is desirable to construct the disks II and springs l3 of a material having good conducting characteristics as well as substantial mechanical strength and it is therefore preferred to use bronze for these parts, but other appropriate materials may be used. The insulating sheath I6 with which the cable is provided is vulcanized to block 18 to prevent leakage of fluid around conductor l1.

Since the device is particularly applicable to logging wells which are filled with an oil base drilling fluid, it is generally unnecessary to provide the springs, telescoping tubes, tip l5 and block IS with electrical insulation because the disks position the rod in the center part of the bore hole and prevent it from making contact with the walls of the hole. The very low conductivity of the oil base drilling fluid causes the current to flow from conductor I I to block l8, then through springs I3 and disks H and hence from the periphery to the disks to the formation. On some occasions, however, it may be desirable to provide springs l3, telescoping tubes l4, tip l5, block I8 and the central portion of disks II with electrical insulation in which case slip rings attached to axles I! will conduct current from conductor IT to disks II and hence the current will flow through the formation.

While I have described a preferred modification of the above invention it will be apparent that other modifications may be used. As stated above, the disks may be provided with sharp projections, such as teeth, or else these projections may be omitted and circular units used. Other flexible mounting means may be used for the disks which will exert a force on them to cause them to penetrate through the filter cake of the bore hole and which will also allow the apparatus to vary in its lateral dimensions to accommodate itself to the varying diameters of a bore hole which may be encountered in use. Then, too, it may at times be desirable to use more than two disks and to change the mountings of the disks accordingly.

I therefore do not intend to be bound by the specific modifications shown herein, but to claim my invention as broadly as the prior art permits.

I claim:

1. A borehole electrode adapted to be attached to the end of an electrical cable for longitudinal movement along a borehole comprising telescoping members, a pair of leaf springs having each end attached to a separate unit of said telescoping members and their central portion spaced away from said telescoping members, a toothed disk mounted on the central portion of each spring for rotation along the longitudinal axis 01' the borehole in which said electrode is placed.

2. A borehole electrode adapted to be attached to the end of a cable for longitudinal movement in a borehole comprising central telescoping members, a plurality of toothed disks each separately attached to said telescoping members through an elastic means, said elastic means biasing said toothed disks in an outward lateral direction.

CECIL J. HAYNES.. 

